THE INSECT WORLD. 



119 



wonderful power of reproduction make the scale especially dan- 

 gerous. 



In the genus Diaspis the scales are more oval, and the cast 

 larval skins are at or near the margin rather than toward the 

 middle, while the 

 males are long and 

 slender. A common 

 example is the Di 

 aspis roses, found 

 on roses and other 

 plants belonging to 

 the same natural 

 family. The scale 

 is pure white and 

 very conspicuous, 

 measuring nearly an 

 eighth of an inch in 

 diameter. 



Yet more oval, 

 with the cast larval 

 skins at the smaller 

 extremity, are spe- 

 cies of Chionaspis, 

 and a good exam- 

 ple is the ' ' scurfy 

 scale, ' ' C. fiirfu- 

 rzis, common on 

 pear and apple. A 

 similar species is 

 found on pine and 

 spruce throughout 



the United States. These species may have one or two gener- 

 ations, according to latitudes, biit ususally winter in the egg state. 



Some of the species have the curious habit of boring under 

 bark, thus passing a large part of their life out of sight, becoming 

 more dangerous by that fact, since trees may be badly infested 

 and the cause of sickness not even suspected by the farmer. 



It is practically impossible to even mention all the injurious 

 scales of house, conservatory, or orchard plants, and it is not 



San Jose scale on a California pear, natural size ; the scale 

 itself enlarged at b. 



